When I pass, no matter which pass I use, I try to anticipate my opponents reaction before I secure side control. For example, if I use the baseball slide, I know that more times than not my opponent is going to shrimp out and usually try to knee shield me. So as soon as I clear the legs with the slide pass, I pop up to knee on belly in order to block the shield.
The other trick I use for the baseball slide is to put my head in the opponents shoulder. This helps in keeping my weight low and staying heavy on the opposite side of my opponent's body, keeping them pinned. Once I slide through, I like to drop my back leg and drive my hip into the mat, similar to a traditional side control. Pressure is key here; become heavy by driving your weight THROUGH your opponent. Use live toes in the mat to generate forward force, and a good cross face works wonders as well. When your opponent starts to react try to stay ahead of them; moving to Kesa Gatame is great to counter the shrimp as long as you can perform it before your opponent creates too much space. When someone shrimps out and creates a lot of space I will usually slide pass back through again then go north-south.
The last tip I have is probably the most important, when passing, assume that your opponent will react in a similar to the way you have been taught. Anticipation of their reaction usually leads me to go north-south as soon as I pass. Once I’m there I get heavy and work back to side control. Don’t forget, good positions create opportunities for submissions.
I hope these tips help, remember to stay consistent and don’t become too frustrated. Hell, if you can’t pass, just hit the foot lock!